Hi James,

Putting an LS into a Toronado transaxle in a Fiero is not necessarily a bad idea, and many enthusiasts do it successfully. Yes, they are relatively cheap and can handle a lot of power, which makes them an attractive option.

But, as with any modification, it's not without its intricacies. If you rotate the transmission and reverse the diff, you could potentially put more of the weight between the axles, helping to balance out the weight distribution which in turn could lead to better handling.

However, the weight is an issue you should consider. As you mentioned, an LS is heavy, and since one of the Fiero's best attributes is its lightness, adding a heavy engine could upset the balance and make it more front-heavy, hurting the car's handling characteristics.

If you're not looking for a race car, but a well rounded vehicle, you might be just fine with this setup. It should still handle decently, and the additional power could be a lot of fun. But keep in mind that this is a significant modification and will require a lot of work, and potential custom fabrication.

Just make sure to do your research and know what you're getting into before you commit to this modification. There will likely be problems that come up during the process, and you need to be prepared to troubleshoot and have some flexibility in your build plan.

Hope this answer helps!